1. Field of the Invention
The present invention relates to optical instruments for measuring the density of a solution.
2. Description of the Prior Art
Refractometers for measuring the refractive indexes of liquids, such as, for example, Abbe-type or Pulfrich-type refractometers, are well known. When using such refractometers, one surface of a transparent member having a known refractive index is brought into contact with a solution to be examined a light is directed towards the surface of the transparent member and its angle of refraction is measured to determine the refractive index. However, these refractometers are not entirely satisfactory since the steps for their use are complicated, involving collecting a fixed amount of the solution to be examined, maintaining the solution stationary and calculating the index. In addition, when the refractive index of the solution varies with time or is converted to an electric signal which is detected by remote control, accurate measurement of the index can be very difficult.
Another known apparatus for measuring the density of liquids by determining the refractive index is disclosed in U.S. Pat. No. 3,977,790 to Schweizer et al. The apparatus utilizes a divergent light ray radiated from a light source into a light-conductive rod, the light ray being non-parallel with the longitudinal axis of the light-conductive rod. When the divergent ray reaches a measuring or incident surface of the rod, the light ray is diffused so as to utilize the total reflection angle on the measuring surface. Therefore, the fact that the light ray is non-parallel with the axis of the rod is advantageous since the light ray can be applied to the measuring surface in a wide range.
An object of the present invention is to eliminate the above-mentioned problems with conventional refractometers.
Another object of the present invention is to provide an optical instrument wherein an accurate measurement of the specific gravity of a solution can be obtained by a relatively easy operation.
Yet another object of the present invention is to provide an optical instrument which is simple in structure and low in cost.
A further object of the present invention is to provide an optical instrument adaptable to a variety of uses.